1. Field of the Invention
The present invention relates to an ink jet recording head for discharging ink to form a desired image on a material to be recorded, and an ink jet recording device.
2. Related Background Art
There has heretofore been known an ink jet recording method comprising: applying heat and other energy to ink; causing a state change with a steep volume change (bubble generation) in the ink; discharging the ink from a discharge port by the action force based on the state change; and attaching the ink to a material to be recorded to form an image, which is a so-called bubble jet recording method. A recording device using the bubble jet recording method is, as disclosed in U.S. Pat. No. 4,723,129, generally provided with a discharge port for discharging ink, an ink channel communicating with the discharge port, and an electrothermal converter as energy generating means disposed in the ink channel to discharge the ink.
According to the recording method, a high-grade image can be recorded at a high speed and with a low noise, and a head for performing this recording method can be provided with highly densely arranged discharge ports for discharging the ink, so that a recorded image with a high resolution by a small device, an easily obtainable color image, and many other superior respects are realized. Therefore, in recent years, the bubble jet recording method has been utilized in a printer, copying machine, facsimile machine and many other office apparatuses, and further utilized in industrial systems such as textile printing equipment.
Additionally, a recording element for generating an energy to discharge the ink can be formed using a semiconductor manufacture process. Therefore, the head utilizing the bubble jet technique is constituted by forming the recording element on an element substrate formed of a silicon substrate, and bonding onto the element a top plate provided with a groove for forming the ink channel and formed of polysulfone, another resin, glass or the like.
Moreover, since the element substrate is formed of the silicon substrate, not only the recording element, but also a driver for driving the recording element, a temperature sensor used for controlling the recording element in accordance with a head temperature, a drive controller, and the like are constituted on the element substrate.
One example of the head substrate is shown, for example, in FIG. 25. Additionally, FIG. 25 shows the constitution as the related art of Japanese Patent Application Laid-Open No. 7-256883.
In FIG. 25, an element substrate 900 is provided with: a plurality of heaters (recording elements) 901, arranged in parallel, for applying a discharging heat energy to the ink; power transistors 902 for driving the respective heaters 901; a shift register 904 to which image data serially inputted from the outside and a serial clock synchronous with the data are inputted, and which latches the image data for each line; a latch circuit 903 for latching the image data for one line outputted from the shift register 903 in synchronization with a latching clock, and transferring the data in parallel to the power transistor 902; a plurality of AND gates 915, disposed for the respective power transistors 902, for applying the output signal of the latch circuit 903 to the power transistor 902 in response to an enabling signal from the outside; and input terminals 905 to 912 for inputting the image data, various signals, and the like from the outside.
Moreover, the element substrate 900 is provided with a temperature sensor for measuring the temperature of the element substrate 900, a resistance sensor for measuring the resistivity of the respective heaters 901, or another sensor 914.
The head constituted by forming the driver, temperature sensor, drive controller, and the like on the element substrate is practically used, and contributes to the enhancement of a recording head reliability and the reduction in size of the device.
In this constitution, the image data inputted as a serial signal is converted to a parallel signal by the shift register 904, and outputted/held by the latch circuit 903 in synchronization with the latching clock. When a drive pulse signal (enabling signal for the AND gate 915) of the heater 901 is inputted via the input terminal in this state, the power transistor 902 turns on in accordance with the image data, an electric current flows in the corresponding heater 901, and the ink of a liquid channel is heated and discharged as a liquid drop from a nozzle tip end.
Here, in the constitution shown in FIG. 25, a main body device in the ink jet recording device monitors the output of the sensor 914 to detect the resistivity of the heater 901, and changes a power voltage and drive pulse width in accordance with the value, so that a substantially constant energy is applied to the heater 901.
In the ink jet recording device described in the Japanese Patent Application Laid-Open No. 7-256883, for a purpose of reducing the load of the main body device of the ink jet recording device, it is proposed to drive the sensor 914, form on the element substrate 900 the drive controller for controlling the drive pulse width of the heater 901 in accordance with the output from the sensor 914, monitor the resistivity of the respective heaters 901 and temperature sensor in the element substrate 900 and detect head property and state and to change the drive pulse width of the heater 901 in accordance with the property and state.
In recent years, for the ink jet recording device, there has been an increasing demand for a higher grade image output in various products and fields. Moreover, a demand for enhancing a recording speed has also increased, and the increase of the number of nozzles for discharging the ink and the shortening of a recording period have been achieved. As a result, the number of the recording elements to be simultaneously driven increases, cost increases because of a necessity of increasing a power capacity, and additionally in respect of fluid the simultaneous discharge of much ink is disadvantageous in performing a stable discharge.
To cope with the problem, it is effective to reduce the number of simultaneously driven recording elements by shortening the width of the drive pulse signal applied to the recording element.
Here, in the conventional example, a head discharge frequency is about 10 KHz (period of 100 xcexcS), and about 6 xcexcS per time division in case of a time division number of 16. In this case, one heat signal pulse width can be handled at about 4 to 5 xcexcS. Here, when the time resolution necessary for generating and controlling a heat signal pulse in the head is of the order of 1/20 to 1/40 of the heat signal pulse, the feedback to the pulse width by the sensor output can be performed, and the clock frequency as a reference for obtaining the resolution is in a range of 5 to 10 MHz (period of 0.2 xcexcS to 0.1 xcexcS).
Moreover, when the width of the heat pulse signal is shortened to cope with the increase of a momentary current by the increase of the nozzle number, and the high printing speed, for example, at the drive frequency of 30 KHz and the time division number also of 16, one time division time is only about 2 xcexcS, and the time for one time division is much shorter than the conventional time of about 6 xcexcS. Therefore, in this case, one heat signal pulse width is requested to be set to 2 xcexcS or less (about 0.5 to 1.5 xcexcS). The resolution required for the heat signal in consideration of the pulse width control is in a range of 0.01 xcexcS to 0.07 xcexcS, and the reference clock signal for satisfying this level of the resolution requires a frequency of 15 MHz to 100 MHz (period of 0.07 xcexcS to 0.01 xcexcS).
When the transfer clock frequency of the image data is increased (the period is shortened), the resolution can be enhanced, but the clock signal is usually supplied to the head from the main body device of the recording device as shown in FIG. 25, and the head moving during printing is therefore connected to the main body device with the relatively long cable of a flexible substrate or the like. Since a high current flows in the vicinity of the cable, noises are easily superposed onto the signal transmitted by the cable, and there arises a phenomenon in which pulse waveform rising and falling are lengthened by the inductance component of the cable (waveform gets blunted) (specifically, the waveform of FIG. 26A changes to that of FIG. 26B). This varies the drive time of the recording element. Moreover, when the drive pulse signal period becomes shorter, the variation proportion relatively increases, the influence of the blunted pulse waveform cannot be ignored, the signal cannot accurately be received on a head side, and there is a possibility that malfunction occurs. Moreover, this also shortens the life of the recording element.
Furthermore, when a high-frequency clock is transmitted, the cable acts as an antenna and radiation noise is generated. This radiation noise possibly causes the malfunction in peripherals.
There is a limitation in the increase of the clock frequency to shorten the conventional pulse width in this manner, and it has heretofore been difficult to set the pulse width to 2 xcexcS or less.
As a technique of eliminating the bluntness of the transfer clock waveform and reducing radiation noises, for example, there is proposed a method of radiating signal light to a carriage with a head mounted thereon from a main body device, receiving the signal light on a carriage side to regenerate an electric signal, and thus transmitting a clock to the carriage from the main body device by so-called optical communication.
In this case, however, since the head and carriage move in accordance with the size of the material to be recorded, the signal has to be correctly received in any position. For this purpose the main body device on a transmission side has to radiate intense light in a wide range, and has to turn on/off the light at a high speed. Specifically, since the main body device needs to pass a large current to a light emitting element for use in the optical communication, and the drive element needs to be switched at a high speed, it is difficult to transmit the clock for the head with the increased speed and increased nozzles via light.
The present invention has been developed to solve the above-described related-art problems, and an object thereof is to provide an ink jet recording head and an ink jet recording device which inhibit the bluntness of a pulse waveform by the transmission of a signal via a cable, and a radiation noise generated from the cable, and which cope with high speed and a multiplicity of nozzles.
To achieve the above-described object, according to one aspect of the present invention there is provided an ink jet recording head comprising: a plurality of recording elements for applying an energy to discharge ink; a recording element driver for driving the plurality of recording elements; a control circuit for controlling the recording element driver; and a high resolution reference signal generator using a plurality of input signals continuously given from the outside in a predetermined period and generating a reference signal which has a period shorter than the predetermined period, so that recording control is performed by supplying the reference signal to the control circuit.
According to another aspect of the present invention there is provided an ink jet recording device comprising: an ink jet recording head comprising a plurality of recording elements for applying an energy to discharge ink, a recording element driver for driving the plurality of recording elements, and a control circuit for controlling the recording element driver; a carriage on which the ink jet recording head is detachably mounted and which is scanned along the surface of a material to be recorded; and a main body device for transmitting a plurality of signals to be used for a recording control to the ink jet recording head. In the ink jet recording device, the ink jet recording head comprises a high resolution reference signal generator for using an input signal continuously given from the outside in a predetermined period and generating a reference signal having a period shorter than the predetermined period, and the recording control is performed by supplying the reference signal to the control circuit.
In the above-described ink jet recording device, since a part of signal period for use in the recording control inside the ink jet recording head can be provided with a high resolution, the period of the signal to be transmitted to the ink jet recording head in which high speed and a multiplicity of nozzles are realized can be set to be substantially the same as the conventional period.
Additionally, xe2x80x9cdownstreamxe2x80x9d and xe2x80x9cupstreamxe2x80x9d used in the description of the present invention are used as representations regarding a liquid flow direction toward the discharge port from a liquid supply source via a bubble generation area (or a movable member), or regarding the upward direction of the constitution.